Sick betta symptoms, by what you can see
Most of what looks like a disease in a 5-gallon is a water result. This page separates the two, in the order a keeper actually meets them.
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The answer, before anything else
Test the water first. In a tank under ten gallons, most of what gets treated as a disease is a water-quality result, and the test is the step that tells you which one you have. An ammonia, nitrite and nitrate reading takes five minutes and changes what you do next more than any observation of the fish does. If ammonia or nitrite is above zero, that is the problem, and no medication treats it.
Then match what you can see to the table below. Three symptoms point at something specific enough to act on: white spots the size of salt grains, fins that are visibly receding or reddened at the edge, and a fish that cannot hold its depth. Everything else on the list is a general sign of stress, and general signs do not select a medication.
What to own before anything is wrong: a liquid test kit, a box of aquarium salt, and nothing else. A medicine cabinet bought in advance mostly expires unopened, and the two items above cover the first response to almost everything here. The third pick on this page is for one specific, identifiable disease, and it is the only one worth buying on sight of the symptom.
What this page is not
It is not a diagnosis. We are not veterinarians, we have not seen your fish, and a photograph genuinely cannot distinguish fin rot from a fin torn on decor - which is why that distinction gets its own paragraph below rather than a confident answer. Where a symptom has several causes, this page lists them all instead of picking the one that sells something. What we refuse to claim covers why.
The symptom table
Read the left column for what you can see, and the right column for what it narrows the cause down to. The third column is the first action, and in five of the ten rows that action is a water change rather than a purchase.
| What you see | What it usually means | First action |
|---|---|---|
| Fins held tight to the body, not spread | Non-specific stress. Most often a water parameter, a temperature below the range a betta holds, or flow the fish is fighting | Test the water; check the thermometer; look at the filter outflow |
| White spots like grains of salt, on fins and flanks, raised rather than patchy | White spot disease. This is the one symptom on the list specific enough to medicate on sight | Treat at the published dose - and move snails and shrimp out of the tank first |
| Fin edges receding, blackened, reddened or looking melted | Fin rot, or mechanical damage that is not healing because the water will not let it | Fin rot, in detail - clean water first, salt second, medication third |
| Floating at the surface, sinking, or swimming nose-down | Buoyancy failure, most often following constipation from overfeeding | Swim bladder and bloating - stop feeding before anything else |
| Belly visibly swollen, scales still flat | Overfeeding or constipation, in most cases | Fast the fish; do not medicate a full stomach |
| Scales standing out from the body, pine-cone shaped from above | Fluid retention from internal organ failure. The prognosis is poor and honesty is more useful here than a product | Isolate, keep the water pristine, and expect that treatment usually fails |
| One or both eyes protruding | Swelling behind the eye. Sustained poor water quality is the common cause; injury and bacterial infection are the others | Test the water; correct it; treat only if it worsens in clean water |
| Sitting on the bottom, barely moving, color faded | Non-specific. Cold water, ammonia, or an old fish - a betta slows down markedly in its last months | Thermometer, then test kit, then how old the fish is |
| Refusing food for more than two days | Often a new tank, a new food, or water too cold for the fish to digest. Rarely a disease on its own | Check temperature first - a betta below the low seventies stops eating |
| Hanging at the surface, gulping | Usually normal - a betta breathes air. Occasionally low oxygen or gill irritation from ammonia | The surface-sitting page works through which it is |
Why half of this table ends in a water change
A 5-gallon tank holds about 4.3 gallons of water once substrate and hardscape are in it. One betta produces a small, continuous ammonia load into that volume, and the margin between a tank that is fine and a tank that is poisoning its occupant is a few days of a filter not keeping up. In a 55-gallon the same lapse is diluted into irrelevance.
This is the single most useful thing to understand about nano-tank fish health: the tank is the patient more often than the fish is. Clamped fins, faded color, hiding, refusing food, sitting on the bottom - all five appear in every water-quality failure and in half the diseases, which is precisely why they cannot be used to choose a treatment. The test kit resolves the ambiguity that the fish cannot.
The corollary matters too. If ammonia and nitrite read zero, nitrate is low, the temperature is steady in range and the fish is still unwell, then you are looking at something the water did not cause, and a medication becomes a reasonable step rather than a guess.
The one case where a photograph genuinely cannot tell you
A betta with shortened, ragged fins has either an infection eating them or a mechanical tear from decor, and the two look alike in every photograph anyone has ever posted. We have said so twice elsewhere on this site and we will not pretend otherwise here.
What distinguishes them is change over time, not appearance in one moment. A tear has a clean edge and a date: it was not there last week, and it gets smaller as the fin grows back. Rot advances - a little more gone each day, often with a dark or reddened margin where healthy tissue meets damage. So the honest instruction is to photograph the fin today, fix the water, and look again in three days. That single step prevents most of the unnecessary medicating that happens in this hobby.
And if it is a tear, the thing to fix is the tank, not the fish. Rigid plastic decor and a filter intake are the two usual culprits - which fake plants are safe and a sponge over the intake are the two cheapest preventions on this site.
What we would actually keep in the cabinet
- 01
A liquid test kit, bought before anything is wrong
This is the only item on the list that is useful on a day when the fish is healthy, because it is how you learn what your tank's normal looks like. Test strips are faster and read ammonia less reliably; the comparison is on the test-kit page. - 02
Aquarium salt, which costs about six dollars and keeps forever
The first response to fin damage and general stress, dosed from the published rate. API publishes plainly that it is not a complete disease treatment, which is exactly how it should be used - alongside clean water, not instead of it. - 03
One medication, and only for a symptom you can identify
White spots are identifiable; clamped fins are not. We keep the white-spot treatment because the symptom is unmistakable and the published dose is unambiguous. We do not keep a general-purpose antibacterial waiting for a reason to use it. - 04
A second container, which is not a purchase
A clean jar or tub, a heater-free twenty minutes and some tank water is what a quarantine or a bath actually requires. Nobody needs to sell you a hospital tank for a 5-gallon.
Before you dose anything, check what else lives in the tank
This matters more on this site than on most, because we recommend snails and shrimp as betta tank mates. API publishes that it does not recommend Liquid Super Ick Cure in any aquarium containing invertebrates, and names snails and shrimp in its own FAQ. The invertebrates come out into a separate container before the first dose goes in, not after somebody notices.
For the antibacterial medications the position is worse: API publishes nothing either way about snails or shrimp on the Fin & Body Cure or Melafix pages. An absence is not a safety clearance, and we treat it as a reason to move the invertebrates regardless.
What we cannot tell you
Which disease your fish has. We can tell you which symptoms are specific enough to act on and which are not, and we can tell you what each manufacturer prints about its own product. Past that point the honest answer is an aquatic veterinarian, and there are more of them than this hobby assumes.
We also cannot tell you how long to keep a tank salted. API publishes a dose and no ceiling on duration, and the ten-day limit repeated across the forums is not on any label we could find. Where the manufacturer declines to publish a figure, we record the absence rather than inventing the number.
What we would buy for this
Chosen from the same registry as our roundups, on published specifications and the arithmetic they imply - not on testing we have not done.
API Freshwater Master Test Kit
The liquid test kit the whole hobby ends up owning, and the only product on this site that can actually tell you whether your tank is cycled. It reads pH, high-range pH, ammonia, nitrite and nitrate, and API publishes over 800 tests per kit - which in a nano tank you will be years getting through. The nitrate test is the one people get wrong: bottle two needs banging on a hard surface for a full 30 seconds or it reads low.
Best for: Anyone cycling a tank, which is anyone setting one up
Skip it if: You want a two-second answer. This is five test tubes, a dropper count and a five-minute wait, and strips are the product for that.
API Aquarium Salt, 36 oz
The first thing to reach for and the cheapest, and API is unusually straight about its limits. The published dose is one rounded tablespoon per 5 US gallons, or half a rounded teaspoon per gallon, and because salt neither evaporates nor filters out, API's own direction is to add it only with a water change rather than topping it up. API also publishes two sentences the forums drop: that it does not change hardness or pH, and that it is "not a holistic solution to heal and treat fish diseases". Treat it as the supporting measure it is sold as, on top of clean water, and it is the best six dollars in a betta cabinet.
Best for: The first response to ragged fins, and the one thing worth owning before anything is wrong
Skip it if: Your tank is heavily planted and you are not prepared to lose plants. API publishes a plain caution to take extra care with live plants, and in a 5-gallon there is nowhere for the salt to dilute to.
API Liquid Super Ick Cure, 1.7 oz
White spots the size of salt grains on fins and flanks are the one betta symptom with a specific, published treatment, and this is it. API prints the dose (1 tsp per 5 gallons), the schedule (repeat at 48 hours, then 48 hours more, then a 25% change with fresh carbon), the half dose for scaleless fish, and the useful note that raising the tank to 82F speeds the parasite through its cycle. The 1.7 oz bottle is the right size for a nano tank. One warning dominates everything else and is easy to miss: API does not recommend this product in any aquarium containing invertebrates, and its FAQ names snails and shrimp specifically. On this site that rules it out of a great many betta tanks, and the tank mates have to come out first.
Best for: Confirmed white-spot disease in a betta-only tank, dosed at the published rate
Skip it if: There is a snail or a shrimp in the tank. API's own FAQ excludes both, so the invertebrates have to be moved to a separate container before the first dose, not after it.
Frequently asked
What is the first thing to do with a sick betta?
Test the water for ammonia, nitrite and nitrate, and check the temperature. In a tank under ten gallons those two checks identify the cause more often than anything you can observe about the fish, and they cost nothing if you already own a kit.
Can I treat a betta without knowing what is wrong?
You can change the water, raise the temperature into range and add aquarium salt at the published rate, and those three are defensible without a diagnosis. Dosing a medication without one is not: the antibacterial products carry four-day and seven-day courses, and a course given for the wrong reason costs the fish a week it may not have.
Are clamped fins always a sign of illness?
No. Clamped fins are a stress response, and the commonest causes in a nano tank are water that needs changing, water a few degrees too cold, and flow the fish is working against. All three are fixable without a medication, which is why this symptom sits at the top of the table rather than next to a product.
Do I need a hospital tank for a betta?
Not as a purchase. A clean container, water from the display tank and somewhere warm to stand it is what a bath or a short quarantine needs. The case for treating in a separate container is strongest when the display tank holds snails or shrimp, because most medications either exclude invertebrates outright or say nothing about them at all.
Is Melafix a medication?
API sells it as an all-natural antibacterial remedy and publishes a seven-day course for it, but the product page names no active ingredient and cites no efficacy evidence. We record both of those facts rather than resolving them: it may help, it is cheap, and it should not be the reason a week passes without the water being fixed.
How do I know if my betta is just old?
Fading color, more time resting on the bottom and a slower response to food, developing over months rather than days, in a tank whose parameters test fine. A betta sold at a year old has a published typical lifespan of two to five years in total, and the last few months of it look like a mild version of several entries in the table above.
Where the figures on this page came from
- Seachem Prime - published dosing directions
- Seachem Stability - published dosing directions
- Aquarium Co-Op, Betta Fish Care Guide - published temperature and tank-size guidance
- API AQUARIUM SALT - published directions, sizes and the manufacturer's own statement that it is not a complete disease treatment
- API LIQUID SUPER ICK CURE - published dosing, 48-hour schedule, scaleless-fish half dose and the invertebrate warning
- API FIN & BODY CURE - published indications, four-dose course, packet dosing and Proposition 65 warning
- API MELAFIX - published indications, 7-day course and dosing (the page names no active ingredient and publishes no efficacy evidence)
- API Freshwater Master Test Kit - published product listing